Solvation method for manufacturing high strength caseless cartridges

ABSTRACT

CASELESS CARTRIDGES OF HIGH PHYSICAL STRENGTH ARE PREPARED BY CONTROLLED SOLVATION OF SMOKLESS POWDER WITH A SOLVATING SOLUTION. THE SOLVATING SOLUTIN IS A MIXTURE OF A SOLVENT FOR THE SMOKLESS POWDER AND A NON-AQUEOUS CARRIER LIQUID WHICH IS MISCIBLE WITH THE SOLVENT BUT IS A NON-SOLVENT FOR SMOKLESS POWDER.

United States Patent 3,576,926 SOLVATION METHOD FOR MANUFACTURING HIGH STRENGTH CASELESS CARTRIDGES John J. OMara, Flauder, N.J., assiguor to Hercules Incorporated, Wilmington, Del. No Drawing. Filed Mar. 28, 1968, Ser. No. 717,001

Int. Cl. C06b 21/02 US. Cl. 264--3 12 Claims ABSTRACT OF THE DISCLOSURE Caseless cartridges of high physical strength are prepared by controlled solvation of smokeless powder with a solvating solution. The solvating solution is a mixture of a solvent for the smokeless powder and a non-aqueous carrier liquid which is miscible with the solvent but is a non-solvent for smokeless powder.

This invention relates to a method of molding of high strength caseless cartridges from smokeless powder employing controlled solvation of the smokeless powder with a solvating solution.

Propellant charges and in particular, caseless cartridges have been prepared from smokeless powder by various molding methods. In one prior art method, caseless cartridges have been made by compressing dry granulated smokeless powder and then solvent dipping or coating the cartridge to harden its surface. Cartridges produced by this method have suitable surface strength but the overall strength of the round is very poor, resulting in frequent breakage of the cartridge. Another approach in the manufacture of caseless cartridges, involves compressing granular smokeless powder in the presence of binder solutions prepared from binders of nitrocellulose, epoxies, or various plasticizers, whereby the binder solution bonds the smokeless powder granules together. Cartridges produced by this method have not been completely satisfactory due to encapsulation of the propellant granules which often results in a failure of the cartridge to breakup on initiation of the primer and burn as a granular propellant charge. Furthermore, the binder acts as a deterrent coating making ignition of the cartridge difficult. The binder also changes the composition of the resulting caseless cartridge. Still another method known in the art for molding of smokeless powder granules involves contacting smokeless powder with an aqueous solvating solution. Cartridges produced employing this method are too weak, to withstand normal handling operations required of ammunition wtihout excessive physical damage to the cartridge.

It is an object of this invention to provide a method for producing caseless cartridges which have sufficient physical strength to withstand normal handling operations and temperature extremes required of ammunition Without damage to the cartridge and, which will break-up upon ignition of a primer to burn as a granular propellant charge.

It is another object of this invention to provide a method for fabricating caseless cartridges which have reliable ballistic reproducibility.

It is a further object of this invention to provide a method for making caseless cartridges from smokeless powder wherein the resulting caseless cartridge is of the same composition as the smokeless powder from which it is made.

Other objects of this invention will in part, be obvious and will in part, appear hereinafter. For a complete under standing of the nature and objects of this invention, reference is made to the following detailed description.

Broadly, in accordance with this invention, there is provided a method for fabrication of caseless cartridges which comprises wetting granules of smokeless powder with a solvating solution, compressing the wetted smokeless powder into the desired shape whereby an agglomeration of smokeless powder granules is formed, drying the agglomeration of smokeless powder granules and recovering a caseless cartridge.

The solvating solution which is employed to wet the smokeless powder granules is comprised of a solvent for the smokeless powder, and a non-aqueous carrier liquid which is miscible with the solvent for the smokeless powder but which is a non-solvent for smokeless powder. Controlled solvation is achieved through wetting the smokeless powder with the solvating solution.

Suitable solvents for the smokeless powder include acetone, methyl ethyl ketone, isopropyl methyl ketone, diethyl ketone, propyl methyl ketone, isobutyl methyl ketone and the like. Mixtures of two or more of the above solvents can be employed, if desired.

Suitable non-aqueous carrier liquids which are miscible with the smokeless powder solvent but which are nonsolvents for the smokeless power include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and the like. Mixtures of two or more carrier liquids can be employed, if desired.

Solvating solutions are prepared by admixing of the smokeless powder solvent and carrier liquid. The solvating solution composition allows for controlled solvation of a granular smokeless powder mass without its agglomerating or sticking. The solvating solutions are comprised of from about 15% to about 65% by weight of solvent and from about 85% to about 35% of carrier liquid based on the weight of the solvating solution. The preferred compositional range for the solvating solution is from about 25% to about 50% of solvent and from about to about 50% of carrier liquid.

The amount of solvating solution employed should be sufficient to uniformly wet the smokeless powder granules and to provide for surface softening of the granules. Suitable weight ratios of solvating solution to smokeless powder are about 0.5/1.0 and above. While smaller amounts of solvating solution can be employed, it be comes difiicult to ensure that each granule is uniformly wetted using smaller amounts. In order to achieve uniform softening it is generally preferred to completely cover the smokeless powder granules with solvating solution. The contact time of the smokeless powder with the solvating solution, when the smokeless granules are completely covered with solvating solution, will vary from about 5 seconds to about 2 minutes, depending on the solvent employed, the concentration of the solvent in the solvating solution, and the size of the individual smokeless powder granules. Longer contact times are requlred when employing solvating solutions containing low percentages of solvent, and when employing larger size smokeless powder granules.

Following the wetting of the smokeless powder granules, the solvent solution is drained from the granules. The wetted smokeless powder granules are then charged to a mold of the desired configuration and compressed. In an alternative wetting method, the granules can be charged directly to a mold, covered with solvating solution, and compresed. Solvating solution is driven out of the mold during compression.

The compression pressure required to form a caseless cartridge is that needed to provide good contact between the solvent wet smokeless powder granules. A preferred pressure range is, however, from about 500 p.s.i. to about 3000 p.s.i. Pressures as high as 13,000 p.s.i. have been utilized without adverse effect on the granules comprising the caseless cartridge. The time at which the granules must 3 4 be held under this compression pressure is on the order invention is clearly demonstrated. Compression strength is of seconds, about ten seconds being satisfactory when increased about 840% and tensile strength is increased operating within the preferred pressure range. Longer about 3600% for the caseless cartridge produced employcompression times are required at pressures less than 500 ing the process of this invention. p.s.i. The following examples are used to illustrate ballist c Following compression of the smokeless powder granresults obtained from firing caseless ammunition where n ules the pressure is released and the resulting cartridge of the caseless cartridge is prepared 'by the process of this agglomerated smokeless powder granules is removed from invention. the mold. This cartridge is dried to remove any solvating EXAMPLES 2-7 solution which may be adhering to the cartridge. The cartridge can be heated at a temperature of from about caseless cartrldges are P p by II1 1d1ng of double 120 F. to about 160 F. to aid in the removal of the basesmokeless p w granules p y p e solvating solution. The time required for removal of the Condltlons Set forth 111 Example The Solvatlng Solutlon solvents will vary with the volatility of the components employed conslsts 0f 40% acetone f f ethanol TWO comprising the solvating solution but in general, will b dilTerent smokeless powder compositions are used. Casefrom about 24 hours to about 96 hours less cartridges are prepared to fit 5.56 mm., 7.62 min., The dried caseless cartridge recovered following the mm, and p {13861655 caftrldgesafe process of this invention is hard and strong. The cartridge assembled bullets and condltlonefi for test fiflngcan be contour machined, if desired, to fit any appropriate Tablin contams data assembled caseless gun chamber, or it can be used directly without machining 20 mumtlon, and test firmg Condltlonsif made in an appropriate size mold. Caseless cartridges TABLE II can be made by the method of this invention for very large caseless weapons since fabrication of the cartridge is dependent Wea on le s t sigoke cartridge, gulllet, on solvation of the smokeless powder by the solvating so- Ex. 5 F f fi az i gi l i lution rather than on compression pressure. Only sufiicient +70 A 5 a1 55 0 rams compression pressure to cause good granule contact is A g f 5 required. +gg 42.0(gralns 150.5)J grains.

The following example further illustrates this inven- 1 B 755 25 1 5": tion. All parts and percentages are by weight unless other- B 115.0 grams-n 8 grams- WiSE specified. NorE.Oo rnposlti on A; 84.15% Nitrocellulose, 15.0% Nitroglycerin. Example 1 Illustrates the hlgh Physical r of hitZsiQtitiftit% i .t2ai.% iti2i bra-eateries:032a less cartridges molded y the Process of thls lnventlon- Moisture and Volatiles. These granules are coated with 5% by Weight of ethyl cellulose and graphite glazed.

EXAMPLE 1 Ballistic data from firing of the caseless ammunition About 100 parts of smokeless powder contammg 91% of Examples 2-7 indicate good ballistic reproducibility.

IllllI'OC6l1l1lOS8 lS charged to 3. A solvating SOlIllIlOIl There are no cartridge failures from any of the tests pomprised 0f 0 parts 9 acetone n parts of ethanol conducted. Ballistics are reproducible for rounds conis prepared. The solvating solution is added to the mold dition d to F. prior o firing, illustrating no breakand completely covers the smokeless powder grflH up of individual granules even at this temperature.

The granules are molded at about 1500 p.s.i. Solvent IS 40 Table -III illustrates muzzle velocities recorded from driven from the mold during compression. Total Contact test firing of the caseless ammunition specified in Table time of propellant granules and the solvating solution is 11. Chamber pressures are recorded for Example 6. These about one minute. The resulting cartridge is dried at 140 ballistic data are substantially the same as if a charge of F. to remove all traces of solvating solution. individual smokeless powder granules were employed The above preparation of a caseless cartridge is re- 5 illustrating good break-up of the cartridge on firing into peated, three times, the only change in the process being individual granules of smokeless powder. The integrity that aqueous solvating solutions of varying compositions of the individual granules of smokeless powder is also are employed in place of the non-aqueous solvating soluillustrated by the fact that no excessive pressures were tion of this invention. recorded in any of these tests.

TABLE III Round Muzzle velocityflcet per second) 1 2 3 4 5 6 7 8 9 10 3,332 3, 057 2, 828 2, 492 3,687 7- 3, 863 3, 794 3, 351 Chamber Pressure (pounds per square inch) Examplefi 50,300 50,300 52,500 51,000 Measurement by Copper Crusher Guage.

The solvating solution compositions, and compression The smokeless powder compositions which can be emand tensile strengths resulting from physical testing of the ployed to form caseless cartridges include single base, caseless cartridges produced are compared in Table I. double base, and triple base compositions.

TABLE I 65 By the term smokeless powder it is meant herein, the

'Well-known colloided nitrocellulose powders, the nitro- Aqueous I cellulose in all events being characterized by a nitrogen Solvatmg S111t1n composltmn aqueous 1 2 3 content of at least about 11.3 weight percent, generally Acetone,percent 40 40 40 40 in the range of from about 12-135 percent, and being Alcohol, percent waterypement 60 40 20 in colloided form. As is well known the single base Compression 3 h p- 4.987 592 20 192 powder contains colloided nitrocellulose as the chief Tensllestrengthp's'l 1010 28 21 4 component, say in the order of from about 85 to 99 From the results of the above tests the physical strength Weight Percent and the double base Powdfir Contains the superiority of the propellant charge prepared by the procsame colloided nitrocellulose component but together ess employing the non-aqueous solvating solution of this with nitroglycerin or an equivalent liquid explosive nitric ester. Double base powders contain generally, at least, one-third colloided nitrocellulose and substantially the remainder nitroglycerin, with, of course, the usual supplemental ingredients. Triple base powders contain nitroguanidine in addition to the colloided nitrocellulose, and nitroglycerin, in proportions generally, at least, about 40 to 50 percent nitroguanidine and substantially as the remainder colloided nitrocellulose and nitroglycerin, the latter two being in any suitable relative proportions, for example, 1: 1, to 4:1 of nitrocellulose to nitroglycerin. Minor amounts of supplemental ingredients can be utilized in these powders, particularly stabilizing agents, gelation agents, oxidizer salts in some instances, DNT oil and the like, all of which are well-known in the art.

The term smokeless powder granules as used herein, is intended t'o 'include any shape'or form of sifiall par ticle of smokeless powder such as flakes, strips, pellets, cylindrical grains and the like.

The caseless cartridges produced in accordance with the method of this invention have the same composition as the smokeless powder from which they are prepared, the solvating solution employed being removed during molding and by drying. The individual smokeless powder granules are glued together when their surfaces, softened by the solvating solution, are pressed together during the molding operation. The use of the non-aqueous carrier liquid prevents an excessive amount of softening. Sufiicient solvent action does take place, however, to give a resulting cartridge of agglomerated smokeless powder having high strength, yet capable of breaking-up, and buming as individual smokeless powder granules when ignited. Break-up of the cartridges into individual smokeless powder granules is necessary in order that the ballistics of caseless ammunition are substantially the same as those of case-type ammunition.

As will be evident to those skilled in the art, various modifications can be made or followed, in the light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure, or scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A method for making caseless cartridges from smokeless powder which comprises (a) wetting smokeless powder granules with a solvating solution comprised of a solvent for smokeless powder selected from the group consisting of acetone, methyl ethyl ketone, isopropyl methyl ketone, diethyl ketone, propyl methyl ketone, isobutyl methyl ketone, and mixtures thereof, and a non-aqueous carrier liquid, said non-aqueous carrier liquid selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and mixtnres thereof,

(b) compressing the wetted smokeless powder grantion of smokeless powder granules is formed.

(c) drying the agglomeration of smokeless powder granules to remove solvating solution and,

(d) recovering a caseless cartridge.

2. The method of claim 1, in which the solvating solution is comprised 'by weight of from about 15% to about of solvent and from to about 35% non-aqueous carrier liquid.

3. The method of claim 2, wherein the solvent is acetone and the non-aqueous carrier liquid is ethanol.

4. The method of claim 2, wherein the solvent is acetone and the non-aqueous carrier liquid is methanol.

5. The method of claim 2, wherein the solvent is methyl ethyl ketone and the non-aqueous carrier liquid is ethanol.

6. The method of claim 3, in which the smokeless powder granules are of a single base type formulation.

7. The method of claim 3, in which the smokeless powder granules are of a double base type formulation.

8. The method of claim3, in which 'the smokeless powder granules are of a triple base type formulation.

9. The method of claim 7, in which the wetted smokeless powder granules are compressed at a pressure of from about 500 p.s.i. to about 3000 p.s.i.

10. A method for making caseless cartridges from smokeless powder comprising (a) covering the smokeless powder granules with a solvating solution for from about 5 seconds to about 2 minutes, said solvating solution being comprised of a solvent for smokeless powder selected from the group consisting of acetone, methyl ethyl ketone, isopropyl methyl ketone, diethyl ketone, propyl methyl ketone, isobutyl methyl ketone and mixtures thereof, and a non-aqueous carrier liquid selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and mixtures thereof,

(b) compressing the wetted smokeless powder granules to effect granule contact whereby an agglomeration of smokeless powder granules is formed,

(c) drying the agglomeration of smokeless powder granules, and

(d) recovering a caseless cartridge.

11. The method of claim 10, wherein the solvent is acetone and the non-aqueous carrier liquid is ethanol.

12. The method of claim 10, wherein the solvent is methyl ethyl ketone and the non-aqueous carrier liquid is ethanol.

References Cited UNITED STATES PATENTS 3,260,203 7/1966 Godfrey et al. 149--2X 3,264,993 8/1966 De Fries et al. 1492X 3,280,746 10/ 1966 Brown 149-2X 3,353,438 11/1967 Scanlon et al. 2643X 3,447,983 6/1969 Camp et al. 2643X 3,463,086 8/ 1969 Silva et al. 1492X ules to efiect granule contact whereby an agglomera- 55 LELAND SEBASTIAN Pnmary Examiner S. J. LECHERT, IR., Assistant Examiner U.S. Cl. X.R. 

